/Engine/Source/Runtime/ApplicationCore/Public/GenericPlatform/GenericPlatformApplicationMisc.h
Asyncronously display the platform-specific user selection UI, if supported.
false if the platform does not support a user-selection API, or it is not currently available (the callback will not be called)
static bool ShowPlatformUserSelector ( [FInputDeviceId](API\Runtime\Core\Misc\FInputDeviceId) InitiatingInputDeviceId, EPlatformUserSelectorFlags Flags, FPlatformUserSelectionComplete OnUserSelectionComplete )